For example, to offer various services to the user, a service provider offering services to the user (hereinafter referred to as provider) builds a business system according to application (hereinafter referred to as information processing system), and runs the system. Specifically, the provider builds the information processing system including a search device that searches for measurement data measured by a plurality of sensors (for example, data such as temperature and humidity in a data center). In this case, the search device collects measurement data measured by the plurality of sensors, and stores the data in a storage device. When receiving a search request from the user, the search device extracts data corresponding to the search request from the data stored in the storage device.
In the search device, when the volume of the measurement data measured by each sensor is enormous, due to limits of storage capacity of the storage device and loads on the network, it may be difficult to store all measurement data in the storage device. Accordingly, the provider arranges a plurality of gateway devices on a communication path between each sensor and the search device. Each gateway device stores the measurement data measured by each sensor, and transmits information indicating the stored measurement data (hereinafter referred to as search key information) to the search device. Thus, the search device may refer to the search key information transmitted from each gateway device to identify the gateway device in which the measurement data corresponding to the search request is stored. Accordingly, the search device may search for measurement data the search request without storing all measurement data measured by each sensor in the storage device (Refer to Japanese Laid-open Patent Publication Nos. 2006-268431 and 2006-350511).